A New Unity Power Factor Rectifier System using an Active Waveshaping Technique

Transcription

1 A ew Unity Power Factor Rectifier Sytem uing 173 JPE A ew Unity Power Factor Rectifier Sytem uing an Active Wavehaing Technique Se-Wan Choi and Young-Sang Bae * * Det. of Control and ntrumentation Eng., Seoul ational Univerity of Technology, Korea ABSTRACT Thi aer rooe a new three-hae diode rectifier ytem with a inuoidal inut current at unity ower factor and a regulated and iolated outut voltage at low level. The inherent natural wave-haing caability of the reduced kva olyhae tranformer together with an active current wave-haing technique reult in a ignificant reduction of inut and outut filter requirement aociated with witching rile and EM. The oeration rincile are decribed along with a deign examle and a comarative evaluation. Exerimental reult on a 1.5kW rototye are rovided to validate the rooed concet. Keyword: Permanent magnet ynchronou motor, Parameter meaurement, P-Q circle diagram, ron lo diode rectifier, Wavehaing, Three-hae ower factor correction, Polyhae tranformer 1. ntroduction A front end diode rectifier ha widely been ued in indutrie. Due to inherent nonlinear witching, diode rectifier uffer from large inut current harmonic reulting in many eriou roblem in the ower ytem. There have been many aroache to eliminate the harmonic in the rectifier ytem. A ix-witch PWM rectifier demontrate high inut ower factor, but require comlicated meaurement and feedback control and i in general cotly [1]. A ingle-witch three-hae PFC i imle to control and Manucrit received ov. 26, 2008; revied January 20, 2009 Correonding Author: choi@nut.ac.kr. Tel: , Fax: , Seoul at l Univ.of Tech * Det. of Control and ntrumentation Eng., Seoul ational Univerity of Technology, Korea low in cot, but uffer from high witch current rating and high EM due to dicontinuou mode oeration [2] and therefore, in general, can not be alied to higher ower alication of more than 10KW. A three-hae rectifier emloying three ingle-hae boot PFC circuit with direct couling oerate in continuou conduction mode (CCM) and therefore allow high ower factor and mall EM filter [3]. However, the outut voltage i high due to boot oeration and require the ue of a DC-DC converter tage to get a low voltage uch a 48VDC in a telecommunication ytem. Recently, an 18-ule iolated rectifier ha been rooed to rovide a regulated dc voltage at low level for telecommunication equiment [4]. Thi cheme i attractive in that natural ower factor correction i achieved by a olyhae autotranformer, and control i imle ince current balancing can be obtained by the connection of

2 174 Journal of Power Electronic, Vol. 9, o. 2, March 2009 econdary winding in high frequency tranformer. n thi aer, a three-hae diode rectifier baed on the arrangement of a olyhae autotranformer and an active wave-haing technique i rooed and hown in Fig. 1. The rooed aroach incororate a 12-ule autotranformer and two three-hae diode rectifier, each followed by a full bridge converter oerating at continuou conduction mode. An active wave haing technique i alied to the rooed cheme reulting in inuoidal inut current at unity ower factor. The advantage of the rooed cheme are; Sinuoidal inut current at unity ower factor meeting with EEE519 current ditortion limit. Higher efficiency due to no ue of an intermediate dc-dc converion tage and the ue of a relatively mall number of comonent. Significantly reduced inut and outut filter requirement aociated with witching rile and EM due to the rooed active wave-haing technique baed on the olyhae tranformer arrangement. olated and regulated dc voltage at low level which are alicable to telecom equiment. Suitability for higher ower alication due to CCM oeration in the whole range of load variation. The oeration rincile are decribed along with the reference ignal generation and control method in the following ection. 2. Prooed Active Diode Rectifier Sytem P o [5]. The oerating rincile i illutrated with variou wavefo hown in Fig. 2. ia1 Sa1 ia2 Sa2 ib1 Sb1 il1, ib2 Sb2 il2 ic1 Sc1 ic2 Sc2 From the autotranformer connection, the inut current can be exreed in te of rectifier inut current a [5], (1) ia ia1 + ia ( ic2 ib2 + ib1 ic1) (2) Then, the hae a inut current can be exreed in te of the inductor current and the witching function a, i a { Sa ( Sb1 Sc1) } il1 + { Sa ( Sc2 Sb2) } il2 t can be noted from equation (3) that the inut current i determined by the inductor current. f the inductor current i dc, the inut current would have 12-ule characteritic due to the natural wave-haing caability of the autotranformer. ow, the inductor current i controlled to have a wave hae given in the following, { v (, v (, v ( ) } (3) * K il1 ( Min ab bc ca t (4) 2 2VLL * * 30 il 2 ( il1 ( t ) (5) ω A. Oerating Princile Fig. 1 how the baic configuration of the rooed rectifier ytem that emloy a three-hae autotranformer and two three-hae diode rectifier, each followed by a current ource full bridge converter. The three-hae autotranformer i emloyed to uly two et of three-hae voltage for each diode bridge which lead and lag the inut ource voltage by 15, reectively. The KVA rating of the autotranformer i 0.24P o, and thi coniderably reduce the ize and weight comared to the equivalent -Y tranformer which ha a KVA rating of Fig. 1 Prooed telecom rectifier ytem

3 A ew Unity Power Factor Rectifier Sytem uing 175 hae of the inductor current i a ortion of the line-to-line voltage, hown a a thick line in Fig. 2. Each current ource full bridge converter i oerated in CCM to hae it inut inductor current a given in equation (4) and (5). Modulating the inductor current a uch reult in inuoidal inut current at unity ower factor a hown in Fig. 2. n the mean time the rimary current of the high frequency tranformer i determined by the witching function of the full bridge converter a, ip1( S1( il1( (6) ip2( S2( il2( Then the caacitor inut current can be exreed a, i d ( d1 + d 2 t i ( i ( ) (7) ( i1( + i2( ) A we can ee from Fig. 2 the large low order (6) harmonic in the two diode current add u and do not aear in current i d. Therefore the filter outut caacitance i greatly reduced. The method of generating reference ignal for inductor current i hown in Fig. 3. The normalized wave hae reference, i L1, and i L2, are tored in the look-u table and i ynchronized with a line-to-line voltage by mean of zero-cro detecting and hae locked loo circuit. The magnitude reference for inductor current are alo obtained by a ignal from outut voltage regulation. Fig. 2 Variou wavefo of the rooed cheme Here, K i a cale factor which can be L, k o determined by the ratio between the inut line-to-line voltage V LL and outut dc voltage V o. The deired wave Fig. 3 Control block diagram

4 176 Journal of Power Electronic, Vol. 9, o. 2, March 2009 The inut and outut relationhi on average value of the rooe rectifier ytem are given a, V o 1 2L, av Vd, av 2 (1 D) P o (8) where the oerating range of the duty ratio i 0.5<D<1. The average rectifier outut voltage V d,av become [5], V d, av VLL (9) From equation (8) and (9) the turn ratio of the high frequency tranformer can be determined by, P V >. 397 LL S Vo 1 (10) Alo, the average value of the inductor current become, L, av L, k (11) From equation (8) and (11), the cale factor K can be obtained by, K V o (12) VLL B. Deign Examle A a deign examle for the rooed diode rectifier ytem the following arameter are aumed: Po 12 kw ; VLL 220V ; Vo 48V The outut current o i given by, Po o 250A (13) V o Then, by letting the nominal duty ratio be D 0.6 the turn ratio can be calculated by equation (8) - (10), P : S 8 : (14) Table 1 ummarize the exreion for voltage and current rating of the tranformer and witching device. The current rating of the comonent in the rooed cheme deend on the duty ratio of the witch. The deign value for a 12kW rectifier ytem hown in the deign examle are lited correonding to the exreion. Table 1 Comonent Rating Calculation Comonent Exreion Deign Value (12kW) Autotranformer Full- Bridge Converte r Switch High Frequency Rectifier Diode High Frequency Tranforme r 1- winding 2- winding voltage current voltage current V VA(%) 100 2V o o eak voltage eak current current eak voltage eak current current rimary voltage rimary current V LL 220V o 1 D A V LL o tan15 34V 3 2 L, A 2.9kW (24%) eak eak V o 384V L, k 35.45A L, 2 2V o 15.68A 98V L, k 283.6A L, A V o 384V L, k 35.45A turn ratio : 8 : 1

5 A ew Unity Power Factor Rectifier Sytem uing 177 C. Comarative Evaluation of the Prooed Rectifier n thi ection a comarative evaluation of the rooed cheme and everal other cheme concerning efficiencie, comonent count, and realization effort etc. i given. The cheme conidered for evaluation include ingle-witch PFC, ix-witch PWM rectifier, three ingle-hae PFC [3], and 18-ule rectifier [4]. The aumed oerating condition for evaluation are lited below. The utility ource i ideal with a zero internal imedance. The comonent are ideal, unle ecified otherwie. The ytem arameter given in equation (13)-(15) are ued in the calculation of witch utilization and loe. The witching frequency i contant with f w 30kHz. The maximum eak-to-eak rile of the inductor current i 10% of it value. The intermediate dc voltage are 400V for ingle-witch PFC, ix-witch PWM rectifier and three ingle-hae PFC[3], 260V for 18-ule rectifier, and 307V for the rooed cheme, reectively. technique Comarative Evaluation of Variou Rectifier 6-witch three PWM ingle-hae rectifier PFC[3] ingle-witc h PFC The calculation of witch utilization, and normalized witching and conduction loe i baed on the equation obtained in the literature [7]. The evaluation reult are lited in Table 2. The rooed cheme emloy a low kva(0.24p o ) olyhae autotranformer followed by diode bridge a a front-end, reulting in natural wavehaing characteritic imilar to the 18-ule rectifier. Since it doe not ue witche oerating at high frequency in the front-end converion tage, the ue of an inut filter i not neceary and the requirement for uing an EM filter are reduced. Due to continuou conduction oeration in the dc-dc converter the required EM filter ize i further reduced. The 18-ule rectifier, which alo ha a ignificantly reduced EM filter ize, may need to ue a mall inut filter to meet the EEE 519 harmonic tandard. The rooed cheme how low witch utilization in the dc-dc converion tage. The total number of witche and diode of the rooed cheme i fairly low, and eecially the number of fat recovery diode i the lowet, reulting in lower ower loe and cot. The witching lo of the rooed cheme i aroximately half of that of the 18-ule rectifier while the conduction lo of the rooed cheme i aroximat 18-ule rectifier[4] rooed rectifier configuration ac-dc-dc-dc ac-dc-dc ac-dc-dc-dc ac-dc-dc ac-dc-dc number of front-end 1 (0.67) 6 (0.1) 3 (0.18) witche dc-dc 4 (0.24) 4 (0.24) 12 (0.24) 12 (0.12) 8 (0.13) (witch utilization) total front-end witching loe dc-dc total front-end conduction loe dc-dc total total number of diode (number of FRD) 13 (7) 12 (12) 36 (24) 32 (14) 16 (4) inut filter or hae-hifting tranformer Table 2 inut filter inut filter no hae-hifting tranformer (0.2 P o ) hae-hifting tranformer (0.24 P o ) outut filter inductor ye ye ye ye no ening effort & control comlexity medium high high low medium

6 178 Journal of Power Electronic, Vol. 9, o. 2, March 2009 ly double of that of the 18-ule rectifier. Thi i becaue the dc-dc converter emloyed in the rooed cheme i a current-fed tye with the duty cycle ranging between 0.5 and 1 while that of the 18-ule rectifier i a voltage tye with the duty cycle raging between 0 and 0.5. Among the five cheme comared, the rooed cheme i hown to have the highet efficiency due to the following reaon: (1) The total ower witch loe of the rooed cheme i hown to be the mallet, (2) an intermediate dc-dc converion tage i not emloyed in the rooed cheme, (3) the total number of witche and diode i relatively low. (a) nductor current i L1 3. Exerimental Reult A laboratory rototye ha been built and the exerimental reult are rovided. The exerimental wavefo for the rooed cheme are hown in Fig.4. The ytem arameter. (b) Rectifier inut current i a1 For the exeriment are a follow: P o : 1.5kW Suly : 220V(line-to-line, RMS), 60Hz V o : 48VDC Dc link caacitor C o 3300uF, nductor L 1, L 2 5mH Fig. 4(a) how the inductor current i L1 whoe waveform i haed by the full bridge converter. The rectifier inut current i a1, hown in Fig. 4(b), ha 120 of dicontinuou eriod. Thi reult in a near inuoidal inut current, a hown in Fig. 4(c). The meaured THD of the inut current i 3.7%. Baed on thee reult, the exerimental reult agree with the analyi hown in Fig. 2. The validity of the control method i verified. (c) nut currenti a 4. Concluion n thi aer a new diode rectifier ytem for telecom alication i rooed to draw inuoidal inut current at unity ower factor o that the rooed cheme meet with EEE519 current ditortion limit for load with any hort circuit current to load current ratio. (d) FFT of i a Fig. 4 Exerimental wavefo Baed on the natural wave-haing caability of the autotranformer with low kva rating(0.24p o ) the rooed active wave haing technique ignificantly reduce inut

7 A ew Unity Power Factor Rectifier Sytem uing 179 and outut filter requirement aociated with witching rile and EM. The rooed cheme i alo hown to have higher efficiency becaue it doe not emloy an intermediate dc-dc converion tage and ha a relatively mall number of comonent. The rooed cheme ha a regulated and iolated outut voltage at low level and therefore i uitable for telecom rectifier. Exerimental reult on a 1.5kW rototye have been rovided to validate the rooed concet. Reference [1] S. Ohtu and S. Muroyama, K. Yamamoto, A comact, High -Efficiency and High-Power-Factor Rectifier for Telecommunication Sytem, EEE APEC Conf., Vol. 2, , March [2] M. Ratogi, R. aik, and. Mohan, A Comarative Evaluation of Harmonic Reduction Technique in Three-Phae Utility nterface of Power Electronic Load, EEE Tran. on A, Vol. 30, o. 5, , Se./Oct [3] G. Siazzi and F.C. Lee, mlementation of Single-Phae Boot Power Factor Correction Circuit in Three-Phae Alication, EEE Tran. on ndutrial Electronic, Vol. 44, , June [4] F.J.M.,Seixa and Barbi,. A 12kW Three- Phae Low THD Rectifier with High-Frequency olation and Regulated DC Outut, EEE Tran. on Power Electronic, Vol. 19, , March [5] S. Choi, P. Enjeti and. Pitel, Polyhae Tranformer Arrangement with Reduced kva Caacitie for Harmonic Current Reduction in Rectifier-Tye Utility nterface, EEE Tran. on PE, Vol. 11, o. 5, , Set [6] S. Choi, P. Enjeti, H. Lee and. Pitel, A ew Active nterhae Reactor for 12-Pule Rectifier Provide Clean Power Utility nterface, EEE Tran. on ndutry Alication, Vol. 21, o. 6, ov./dec [7] B. Singh, B.. Singh, A. Chandra, K. Al-Haddad, A. Pandey, D.P. Kothari, A Review of Three-hae mroved Power Quality AC-DC Converter EEE Tranaction on ndutrial Electronic, Vol. 51, ue 3, , June [8] Y. ihida, J. Miniboeck, S. D. Round, J. W. Kolar, A ew 3-hae Buck-Boot Unity Power Factor Rectifier with Two ndeendently Controlled DC Outut, EEE APEC Conf., , Feb [9] P. Bozovic, P. Pejovic, Current-njection-Baed 12-Pule Rectifier Uing a Single Three-Phae Diode Bridge, ET Electric Power Alication, Vol. 1, ue 2, , March [10] M. Shigeta, S. Saito, H. Mochikawa, A Develoment of ovel DC 48 V Power Suly Sytem Utilizing 18-Pule Rectified Active DCL and Reonant Converter, Telecommunication Energy Conference, TELEC, , 29 Se.-3 Oct [11] L.C. Gome de Freita, M.G. Simoe, C.A. Canein, L.C. de Freita, Programmable PFC Baed Hybrid Multiule Power Rectifier for Ultra Clean Power Alication, EEE Tranaction on Power Electronic, Vol. 21, ue 4, , July [12] K. Oguchi, T. Kubota,. Hohi, Aymmetrical ine-phae Voltage Ste-u/down Diode Rectifier with 18-te nut Current, EEE ndutry Alication Conference, Vol. 1, , Oct [13] J. Salmon,. Roberge, Performance Aement of 18-Pule 3-Phae Rectifier Uing Harmonic Reducing Auto-tranformer, Canadian Conference on Electrical and Comuter Engineering, , May Se-Wan Choi received hi Ph.D. degree in electrical engineering from Texa A&M Univerity, College Station, TX, in From 1985 to 1990, he wa with Daewoo Heavy ndutrie a a Reearch Engineer. From 1996 to 1997, he wa a Princial Reearch Engineer at Samung Electro-Mechanic Co., Korea. n 1997, he joined the Deartment of Control and ntrumentation Engineering, Seoul ational Univerity of Technology, Seoul, Korea, where he i currently a Profeor. He i an Aociate Editor of EEE Tranaction on Power Electronic and Journal of Power Electronic. Hi reearch interet include three-hae ower factor correction and fuel cell ower converion technologie. Young-Sang Bae wa born in Kunan, Korea, in He received hi B.S. degree in electrical engineering from Hoeo Univerity, Aan, Korea, in 2003 and the M.S. degree from the Deartment of Control and ntrumentation Engineering, Seoul ational Univerity of Technology, Seoul, Korea, in He i currently an Engineer of the Reearch and Develoment Center, KACO Solar Korea. Hi reearch interet include utility interface and ower quality iue including ower factor correction.